BSIM3v3.2 (implemented with SPICE 3F5)
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BSIM3 is a physical MOSFET model with extensive built-in dependencies of important dimensional and processing parameters such as channel length, width, gate oxide thickness, junction depth, substrate doping concentration, and so on. It allows users to accurately model MOSFET behavior over a wide range of channel lengths for present and future technologies. Using a coherent pseudo 2D formulation, major short-channel effects and high field effects such as threshold voltage roll-off, non-uniform doping effect, mobility reduction due to vertical field, carrier velocity saturation, channel-length modulation, drain induced barrier lowering, substrate current-induced body effect, subthreshold conduction, parasitic resistance effect, quantum effects, and LDD effect are included. Meticulous care has been taken to retain the physical functional relationships and achieve a high level of model accuracy and computational efficiency. The effects of variations in these parameters on the device AC and DC characteristics are built into the model. The predictive feature of BSIM3 makes statistical modeling of the device in the presence of fabrication process variations considerally simpler.
BSIM3 is further enhanced in version #3, which retains the physically based and predictive features of BSIM3, but introduces the following features: (a) A single I-V expression describes the current and output conductance characteristics from the subthreshold to the strong inversion, and from the linear to the saturation regions, so that it can guarantee the continuities of Ids, gds, gm, and their derivatives in whole operation regimes of Vgs and Vds, and removes all kinks and glitches at the boundaries between the regions; (b) It introduces new width dependences of bulk charge and Rds, which enhances greatly the accuracy of the model in small W regime; (c) It considers the dependence of dW and dL on channel width W and length L, and can fit the device characteristics in a wide region of W and L with one single set of parameters; (d) It includes a new short-channel capacitance model, which can describe the C-V charareristics of the device with the channel length down to deep submicrometer region accurately; (e) It introduces a new noise model to describe the flicker and thermal noise characteristics more physically; (f) It includes a NQS model option; (g) it also provides a binning option for the users who want to improve the model accuracy further; and (h) quantum mechanical effect.
BSIM3v3.2 has the following enhancements and improvements relative to BSIM3v3.1:
- An original and accurate charge thickness capacitance model considering the finite charge layer thickness (quantum effects). This model is smooth, continuous, and very acurate through all regions of operations.
- Improved modeling of C-V characteristics at the weak to strong inversion transition.
- Adding the Tox dependence into the threshold voltage (Vth) model.
- Adding the flat-band voltage (Vfb) as a new model parameter.
- Improved substrate current scalability with channel length.
- Restructuring of the non-quasi-static (NQS) model, addition of NQS into the pole-zero analysis and fixing bugs in NQS codes.
- Adding temperature dependence into the diode junction capacitance.
- DC diode model now supporting a resistance-free diode and current-limiting feature.
- Option of using the inversion charge of capMod 0, 1, 2, or 3 to evaluate the BSIM3 thermal noise.
- Elimination of the small negative capacitance of Cgs and Cgd in the accumulation-depletion regions.
- Introducing a separate set of channel-width and length dependence parameters (Llc, Lwc, Lwlc, Wlc, Wwc, and Wwlc) to calculate Weff and Leff for the C-V model for better fitting of the capacitance data.
- Adding parameter checking to avoid bad values for certain parameters.
- Bug fixes.
BSIM3v3.2 model is implemented with SPICE3f5.
Software Available at:
- SPICE3F5 User's Guide and Installation Notes. Available separately for $10.00.
- BSIM3v3.2 MOSFET Model User's Manual by Weidong Liu et al., Memorandum No. UCB/ERL M98/51, August 1998. Available separately for $21.40.
- For the source code of the latest BSIM3 model, please go to "C code tarred and zipped file (6-16-98)" at http://www-device.eecs.berkeley.edu/~bsim3/get.html